The study will assess the duration of protection of single doses of 2 different long acting muscarinic antagonists against methacholine induced bronchoconstriction.

Inclusion Criteria:

• male or female asthmatics > 19 years of age
• baseline methacholine PC20 less than or equal to 4mg/ml
• baseline lung function >65% predicted
• non-smoker and less than 10 pack year smoking history

Exclusion Criteria:

• use of anticholinergic within 30 days of Visit 1
• poorly controlled asthma
• pregnant or nursing
• respiratory illness within 4 weeks of Visit 1
• exposure to an agent that triggered asthma worsening (e.g. allergen) within 4 weeks of Visit 1

journal publication